Sewage tank



FIG. 1 is a perspective view of a sewage tank in accordance with the new design;

FIG. 2 is a front elevational view thereof; a rear elevational view being a mirror image thereof; and,

FIG. 3 is a right side elevational view thereof, a left side elevational view being a mirror image thereof.

The broken lines in the drawings are for illustrative purposes only and form no part of the claimed design. 

The ornamental design for a sewage tank, as shown and described. 